Signaling apparatus



Dec. 27, 1938. F. G. TROISI 7 2,141,323

- SIGNALING APPARATUS Filed Dec. 3, 1936 3 Sheets-Sheet l WITNESSES: lNVENTOR zgww . BY d ,A ZQQ 4 g. 7/ a? m 7 ATTORNEY ZZZ/M2520 fig/3:.

Dec. 27, 1938. o s 2,141,323

SIGNALING APPARATUS Filed Dec:v 3, 1956 3 Sheets-Sheet 2 Dec. 27, 1938. F. G. TROISI SIGNALING APPARATUS Filed Dec. 5, 1936 3 Sheets-Sheet 3 INVENTOR WITNESSES:

BY W M ATTORNEY Patented Dec. 27, 1938 UNITED STATES PATENT orrlc SIGNALING APPARATUS Florentine G. Troisi, Pittsburgh, Pa.

Application December 3, 1936, Serial No. 114,012 20 Claims. (c1. 119-1) My invention relates to signaling apparatus and has particular relation to apparatus for transmitting messages and signals between an operator at a central station and a plurality of operators in b distributed stations such as diving suits, for

example.

It is an object of my invention to provide apparatus for transmitting messages from one diver to another which shall be heard by a central station operator and for transmitting both messages and signals from the central station operator to any or all of the divers. 1

Another object of my invention is to provide a simple and inexpensive system for transmitting i3 amplified signals and messages from a central station to any or all of a plurality of distributed stations and from any one distributed station to any or all of the other distributed stations and the central station.

A further object of my invention is to provide apparatus for transmitting signals from a central station to a plurality of distributed stations located in diving suits under water, that shall incorporate an oscillation generator for signaling purposes 25 and in which the oscillation generator shall be so connected as toinvolve no danger to the operator located in the diving suit.

Still another object of my invention is to provide a system incorporating an amplifier for inter- 3i) communications between a plurality of stations that shall be so contrived that it shall be possible to transmit messages between the stations when the amplifier system is for one reason or another out of operation. 1

:3 An incidental object of my invention is to provide a switching element provided with contacts, to be connected to two points at difierent potentials, in which the contacts. shall be rigidly mounted.

4.) Another incidental object of my invention is to provide a plug, of the type that is inserted in a jack to complete an electrical connection, that shall be particularly adapted for making such a connection in a watertight enclosure, and which 43 shall not require accurate positioning of the plug within the jack.

A further incidental object of my invention is to provide a watertight connection for a life-line of the type that incorporates electricalconductors.

50 More specifically stated it is an object of my invention to provide apparatus for signaling between a central station located above water and a plurality of distributed stations located in diving suits under water by the operation of which it 55 shall be possible to transmit clear and audible signals without danger of injury by electrical shock or otherwise to the operators in the diving suits.

According to my invention I provide a signaling system in which self-energizing batteryless sound 5 conversion units were disposed at the distributed stations in the diving suits and preferably at the central station. Sound conversion units of the type that I prefer to utilize are described in my Patent #1370321, dated July 15, 1930, for Telephonic apparatus for deep sea diving. Each of the units includes a diaphragm, an armature, a permanent magnet in the field of which the armature vibrates and a voice coil which varies the field of the permanent magnet to provide a vibratory force. The unit may accordingly be utilized either as a receiver or a transmitter of sound. In the practice of my invention-one of the units is at any time utilized to transmit a message or signal to one or more of the remaining units. The sound impressed on the transmitting unit is amplified before being reproduced; a single amplifier is used for all of the units.

To properly interconnect the sound conversion units and the amplifier a plurality of switches preferably one for each of the distributed stations are provided. The switches are preferably located at the central station and are operated by the central station attendant. The. distributed station switches are operable to connect the 9 sound conversion units at the distributed stations either to the input or the output of the amplifier. When a sound conversion unit is connected to the input of the amplifier the operator at the corresponding station may speak through his sound conversion unit to the operator of any station in which the sound conversion unit is connected to the output of the amplifier. The central station connections are such that the attendant at the central station hears the conversation between '40 the operators at the distributed stations.

Corresponding to the central station a switch' is provided that may be operated by the central station attendant to enable him to talk to the operators in the distributed stations. When the central station switch is in a position for the transmission of messages from the central station, the central station, sound conversion. unit is connected to the input of the amplifier and the distributed station conversion units are connected to the output of the amplifier regardless of whether the switches corresponding to the latter are in a position'for transmission or reception.

Should the central station attendant desire to attract the attention of the divers he throws the 56 central station switch in another direction causing the operation of a signaling oscillation gen- At the same time the sound conversion units at the distributed stations are connected to the output of the amplifier.

If the amplifier should become inoperative for one reason or another the system does not necessarily become inoperative. as has been mentioned above the sound conversion units are of the batteryless type such as are used in soundpowered telephone systems. When the amplifier becomes inoperative the sound conversion units are all connected in parallel and the appa ratus operates sound powered.

In the practiceof my invention plug and jack combinations are utilized for making connections. In accordance with a further aspect of my invention I provide a plug having contacts to be connected to at least two points between which a different of potential exists. The plug is analogous to'those of the prior art, but is of considerably more rigid structure and has other advantages which will be apparent from the following description: 4

.It comprises a central longitudinal member on which cylindrical contact members are disposed. The contact members are separated by cylindrical-insulating members. The surfaces of engagement between the insulating members and the contact members are at an anglediflerent that to the akis of the longitudinal member and therefore lateral motion of the cylindrical contact and insulating member is prevented.

When apparatus constructed according to my invention is used, the plug cannot be locked in a single position since the plug and jack are located under water during normal operation and must be enclosed in a water-tight chamber.. To prevent the contacts of the plug from becoming disengaged from the contacts on the jack, I construct the former contacts with considerable length.

The electrical conductors. whereby the signals are transmitted between the different distributed stations and the central station are imbedded in the divers life-line. The life-line and the conductors are connected to the diving suit through a. water-tight plug assembly which comprises a suitable sleeve into which a nut is screwed compressing packing and washers suitably disposed. The life-line is secured to a block mounted in the sleeve by sealing the core of the life-line in an opening in the block.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation together with additional objects and advantages thereof will best be understood from the following description of specific embodiments when read in connection with the accompanying drawings in which:

Fig. 1 is a view in perspective showingthe essential elements of an embodiment of my invention;

Fig. 2 is a view partly in section and partly in side elevation showing the cable utilized in the practice of my invention and the structure whereby the cable is coupled to the apparatus at its terminals;

Fig. 3 is an exploded view showing the essential features of the apparatus whereby the cable is coupled at its terminals;

'conversion units 41, 49, and 5| located at the 'to three connecting outlets are in use.

Fig. 4 is a view in perspective showing the jack utilized in the practice of my invention;

Fig. 5 is a view in section showing a plug constructed in accordance with my invention;

Fig. \6 is a diagrammatic view showing the circuit utilized in the practice of a preferred embodiment of my invention; and

Fig. 7 is a diagrammatic view showing the principal elements of the circuit utilized in the practice of a modification of my invention. 10

In Fig. 1 the essential aspects of the apparatus located atthe central station 9 and at one of three distributed stations II is illustrated. At the central station a closed container I3 is provided andan amplifyin'gand signaling unit I5 15 together with a plurality of controlling switches i1, i9, 2|, 23, and 25 are located within the container. The switches' are operated by handles which project from the upper surface 21 of the container l3. The cover 29 of the container is suitably hinged to the upper surface thereof and supports a loud speaking sound conversion unit 3|. In the back 33 of the container l3 a plurality of suitable connecting receptacles 35, 31, 39, 4|, and 43 for plugs are provided. Power is supplied to the container l3 by plugging a cable 45 from a suitable power source 46 into one of the upper receptacles 35. The lower receptacles v 39, 4|, and 43 are utilized for connecting sound distributed stations to the central station.

The conductors 53 and 55 connecting the central station 9 and the distributed stations are imbedded in the divers life-line 51 and are connected to plugs 59 at both ends. The plugs 59 are mounted in coupling member 6| at both ends; and when the apparatus is in operation, the plugs are inserted in jacks 63 and the coupling members 6| engage cooperating coupling members 65, 61, 69, and H provided for the receptacles 39, 4|, and 43 and at the distributed stations such as I I. The distributed station coupling member 'H is mounted near the center of the rear of the divers helmet 13. The divers sound-conversion units 41, 49, and 5| are secured within the helmet l3 opposite to the position of the divers month. They are connected to the jacks within coupling member II by a cable 15 which is clamped along the upper portion of the helmet. While the life-line coupling member 6| is tightly screwed to themember H in the helmet I3, the life-line 51 is not suspended from this alone, but passes. through a suitable clamp 11 in the breast plate 19 of the diving suit.

In Fig. 1 a single diving sound conversion unit is shown as connected. The container l3 at the central station is provided with two additional receptacles 39 and 4| adapted to receive cable couplings similar to that shown and in the ordinary practice of my invention any'number up When any of the receptacles 35, 31, 39, 4|, and 43 are not in use they are protected by closed hexagonal caps 8| which are screwed over the receptacles and which, when the receptacles are in use, are 35 suspended from chains 33 extending from .the back 33 of the container l3.

The life-line 51 and, its coupling members 3| are shown in detail in Figs. 2 and 3. The body of the life-line is composed of rubber or other flex- (0 ible insulating material 35 strengthened by a stranded steel core 81 imbedded in its center. The electrical conductors 53 and 55 are imbedded in the insulating material 35 between the core 81 and the outer surface. In the preferred prac lo tice of my invention a pair of conductors is utilized for each terminal connection. The conductors of each pair are connected together at the upper and lower ends. The coupling member 6| comprises a sleeve 89 into which the life-line 51 extends. The sleeve 89 is provided with an inwardly-projecting flange 9I that supports a cylindrical block 93. The block 93 has a conical opening 95 coaxial with the outer surface thereof and, before the plug is disposed on the flange 9|, the stranded cor 81 of the life-line 51 is skinned and projected through the opening where the individualstrands are spread out and disposed around the periphery of the opening 95. A screw 91 is then driven into the core wires and the whole conical opening is filled wlth'solder.

At its lower end 99 the sleeve 89 is threaded internally and directly above the thread, the opening in the sleeve tapers towards a narrow neck IOI that terminates at the flange 9|. Before the life-line 51 is inserted in the sleeve 89 an externally threaded hexagonal nut I03 and a packing gland I05 are slipped over it. When the core 81 has been fastened to the block 93 the block is set on the flange 9I. The packing gland I03 is then inserted in the tapered portion below the neck IM and after the life-line has been pulled taut, the externally threaded nut I03 is engaged with the threads 99. When the nut I03 is screwed tightly, it compresses the packing I05 and renders the lower portion of the lifeline coupling 6I water-tight.

When the end of the life-line 51 that is to be connected to the coupling-member 6| is skinned and otherwise prepared for the connection, it is trimmed in such manner that the conductors 53 and 55 extend considerably beyond the end of the stranded steel core. Hence, when the block 93 is seated on the flange 9|, the conductors 53 and 55 are slipped through grooves I01 milled into the block. The projecting ends of the wires composing each pair 53 and 55 are then twisted together and soldered into the terminal lugs I09.

The plug 59 is in its geometric structure not unusual. It comprises a composite longitudinal cylindrical member II I extending above a flanged portion II3 below which the plug terminals H5 and H1 project. The terminal'lugs I09 are secured to the terminals H5 and H1 and the plug with the lugs attached thereto are disposed within the sleeve 89, the flanged portion II3 resting on a leather washer I29 which in turn rests on an internal flange I2 I' located near the upper end of the sleeve. An insulating washer I I9 insulates the terminal lugs I09 from the block 93 and screw 91. Before the plug 59 and its attachments are inserted in the sleeve 09 the portion of the sleeve between the block 93 and the upper flange I2I is filled with melted wax I23 and the contacts H5 and H1 and the lugs I09 are immersed in wax. The upper'end I25 of the sleeve 89 is threaded and an externally threaded nut I21 is provided to engage this thread. The nut I21 rests on and compresses a. leather washer I disposed on the flanged portion I I3 of the plug 59. The washers I29 and I30 thus render the upper portion of the coupling member 6I water-tight.

In its upper region the sleeve 89 is provided with an external flange I3I. Before the life-line s permanently connected to the coupling member 8i, it is slipped through a ring MI and a nut I33 internally threaded along only a portion of its length I35. In its unthreaded portion I31, the nut I33 is provided with an internal flange I39 which engages the external flange I3I on the sleeve/89 preventing the nut from slipping off the end of the sleeve. After the sleeve 89 is connected to the life-line 51, the nut I33 is raised to a position near the external flange I3I on the sleeve and is prevented from sliding back 'of the sleeve 89 by the ring I4I which is pinned to the outer surface of the sleeve below the nut.

In accordance with my invention the receptacles 35, 31, 39, 4I,-and 43 and the coupling member H are provided with externally threaded cylindrical portions I43 which the nut I33 is adapted to engage. When a plug 59 is to be inserted in one of the receptacles, the nut I33 is screwed onto the threaded cylinder I43 and thus the life-line 5| is tightly coupled to the apparatus to which the plug is connected. When the equipment is not in use it'is desirable that the coupling member 6| be protected and for this reason a cover I45 adapted to be screwed into the nut I33 is added-to the equipment.

The jack 63 utilized in accordance with the practice of my invention is shown in Fig. 4. It comprises a semi-cylindrical block I41 of insulating material such as a phenolic condensation product having an axial opening I49 therethrough and provided on its plane face I5I with a bracket I53 having the form of an E in end view. The legs I55, I51, and I59 of the E are plate-shaped and form grooves parallel to the face I5I. The whole unit may be machined from a rectangular piece of insulating material of the proper dimensions. In machining the element the grooves between the plates I55, I51, and I59 are cut so deeply that they open into the opening I49 and spring contact elements I 6I and I63 secured to the body of the E on both sides extend into the grooves and therefore project into the opening I49. The block I41 is bolted to a metal plate I65 provided with a hollow stem I61, the opening in which is coextensive with the opening I 49. A leather gasket I69 is then slipped in the stem below the plate I61. Jacks similar to that described above aremounted in the receptacles 35, 31, 39, M, and 43 with the gasket I69 outward The plug 59 is "slipped into the jack through the opening in the stem I65 and opening I49 and when the plug is so inserted the upper end of the sleeve 6| and the upper end of the nut I21 coextensive therewith rests against the gasket I69. When the nut I33 is screwed tightly in place, the whole coupling assembly is water-tight. As the gasket I69 wears or gives, the plug 59 may move inwardly or outwardly. Accordingly the plug cannot be of precisely the usual structure which is locked in a predetermined position.

The plug 59 is shown in detail in Fig. 5. It comprises a bolt I1I threaded near the top I 13 and provided with a head I15 at its lower end. The terminals H5 and H1 are of L section and the base I11 of one terminal II5 rests directly on the bolt head I15. On the terminal base I11 an insulating washer I19 is disposed and an insulating tubular member I8I over the bolt extends upward from the washer." The base I83 of the other terminal II1 of the plug 59 issweatedonto a metallic tubular member I85 through which the insulating tubular member I8I is slipped. The two terminals H5 and II 1 are thus insulated from each other.

On the base I83 is an insulatingwasher I81 andan insulating shell I89 extends upward from the washer. A metallic member I99 provided with the comparatively heavy flange H3 is mounted on the insulating shell I9I. The insulating shell I89 is provided at its upper end with a ringshaped projection I 93 having surfaces E95 and 391 at an obtuse angle ttrthe axis of the shell. The conducting member I 9! of the assembly is provided with an upper surface corresponding to the lower surface l9? of the ring 699 and firmly engages the ring at the top. la washer i 81 insulates the flangel it from the terminal H1.

The metallic shell M is not of simple structure. but is provided with a ring-shaped projec tion I99 of wing-cross section which functions as the contact connected to terminal ill. The contact I99 is provided with a bevelled surface at the bottom to correspond to the surface i95 of the insulating ring projection I93. Its upper surface 20I is also bevelled.

The inner insulating member I9I extends to a point within the contact l99. Into the upper portion 203 of the contact I99 the stem 295 of an insulating member 291 of T section which is slipped over the bolt I1I is engaged. The T section member 201 is provided near its center with the ring-shaped cross member 299 having bevelled surfaces at the top and bottom. The lower bevelled surface is designed to engage the corresponding upper surface 20I of the contact I99.'

The upper surface 2| I engages another contact member 2I3 which is threaded to engage the threads I13 on the bolt Hi. The bolt "I is tightly screwed into the upper contact member 2I3 and thus good contact is obtained between the various connecting metallic-elements. The upper contact member is provided with a reamed opening 2I5 into which solder is poured and permitted to harden to make certain that the assembly is rigid. The contact members I99 and 2I3 are both comparatively long so that when the leather gasket I59 mounted on the Jack 53 wears the plug contacts continue to engage corresponding jack contents I6I and I53. I

The preferred electrical circuit utilized in the practice of my invention is illustrated in Fig. 6. Power is supplied to the system preferably from the direct current generator 45 which is customarily present on the tug or boat from which the divers are launched. The generator is connected through a pair of contacts 2I5 of the switch I1 to the terminals of a voltage dividing potentiometer 2I1 whereby the various potentials are supplied to a two-stage amplifier 2I9 and an oscillationgenerator 22I provided for signaling purposes. The switch I1 is also provided with a pair of contacts 223 which connect the output coil 225 of the amplifier system 2I9 through the switch 25 which determines the direction of transmission of the signals and messages. The movable contacts 2I5 and 223 of the switch I1 are operated together and when the switch is in one position engage the corresponding fixed contacts 221 and 229 respectively at the same time. The switch may also be operated to another position where movable contacts 223 engage a pair of fixed contacts 23I connected across the input coil 233 of the amplifier 2I9.

As has been explained the amplifying and signaling unit I5 and the control switches I1, I9, 2I, 23, and 25 are mounted in the container I3 located at the central station while the sound conversion units 41, 49, and 5| are mounted in the helmet II of the diving uniforms. The switches I9, 2|, and 23 are each associated with a sound conversion unit 41, 49, and 5I respectively. Each of these switches I9, 2|, and 23 may be thrown either to the transmit position or to the receive position, thus enabling the operator to control the fiow of messages or signals.

The amplifier 2I9 is of the ordinary two-stage type in which a pair of pentode amplifier tubes 235 and 231 are utilized. The signal or message energy is impressed on the input coil 233 which is the primary of a suitable audio-transformer 5 239. The output circuit 2 of the first stage of the amplifier is' resistance-capacity coupled to the input circuit 243 of the second stage and the output energy of the second stage is delivered through a suitable audio-output transformer 245 of which the coil 225 is the secondary. The usual resistors and capacitors functioning to properly couple the amplifier and to properly supply and filter the required tube potentials are provided,

but they are well known in the art and need not be discussed here.

The apparatus provided in accordance with my invention is utilized principally for transmitting messages. However,'under certain circumstances it becomes necessary to transmit a signal, that is to say, a note of some kind to indicate to the divers that a certain event is'to take place. In accordance with my invention the oscillation generator 22I is utilized to provide the signal note.

The oscillation generator 225 comprises the usual three-electrode tube 241 in the grid circuit 249 of which a resonant network 25I tuned to the frequency of the note utilized is connected. The grid circuit 249, is inductively coupled to the anode circuit 253 through a transformer 255, the primary of which is the 'coil 251 utilized in the tuned network 25I. The secondary 259 of the transformer 255 is connected to the anode 25I of the tube 241 at one terminal and at the other terminal is adapted to be connected to the positive pole 263 of the source 46 when the operators switch 25 is thrown to the signal position.

The output of the oscillation generator 22I is applied to the input of the first amplifier stage through an inductive connection to the primary 40 233 of the input transformer 239. Since the primary of the input transformer may be conductively connected to the sound conversion units 41, 49, and 5| in the diving suits, it is desirable to avoid any direct connection between the anode 23I and the input circuit for the anode is at a dangerously high voltage and accidental connection to the diving; suit may be disastrous. Accordingly a separate output coil 265 is utilized for the oscillation generator and it is completely insulated both from anode circuit 253 of the tube 241 and from the grid circuit 249.

Now assume that the power control switch I1 is in the lower position, that is the position in which the movable contacts 2I5 and'223 engage the fixed poles 221 and 229. Assume also that it is desirable that one of the divers, say the one corresponding to the sound conversion unit 41, desires to talk to the diver corresponding to the sound conversion unit 5I. In such a case the .269, the lower central movable contact 21l on the right of the operators switch 25, a corresponding fixed contact 213, a conductor 215, the upper central movable contactor 211 on the right of the operator's switch, a corresponding fixed contact 219, a conductor 29I, a conductor 283,

the primary 233 of the input transformer 239, a conductor 285, a conductor 281, an upper left hand central fixed contact 2890f the operators switch, the corresponding movable contact 29|, a conductor 293, a lower left hand central fixed contact 295 of the operators switch, the corresponding movable contactor 291, a conductor 299, a movable contact 30| of the transmitting divers switch, the conductor 55 to the lower terminal of the sound conversion unit.

The speech of the transmitting diver is'amplified by the amplifier 2|9 and the output of the amplifier is connected to the sound conversion unit of the receiving diver. The latter circuit extends from theupper terminal of the secondary 225 of the output transformer 245 through a conductor 303, a movable contact 305, of the receiving divers switch 23, the conductor 53, the sound conversion unit 5|, the conductor 55, a movable contact 301 of the receiving divers switch, a conductor 309 to the lower terminal of the output transformers secondary.

It is to be noted moreover that the operator at the central station also hears the conversation between the two divers. This occurs because the secondary 225 of the output transformer 245 is connected to the operators sound conversion unit 3| through the contacts 223 of the switch I1. The circuit for the operators unit 3| extends from the upper terminal of the output secondary 225 through the conductor 303, a conductor 3, a movable contact 223, a conductor 3|3, a conductor 3|5, an upper right-hand fixed contact 3|1 of the operators switch 25, the upper right-hand movable contact 3|9 of the operators switch, a conductor 32l, the operators sound conversion unit 3|, a. conductor 323, the upper left-hand movable contact 325 of the operators switch, a corresponding fixed contact 321, a conductor 329, a conductor 33|, a movable contactor 323, a conductor 333, the conductor 309 to the lower terminal of the secondary of the output transformer.

It is to be noted that when the divers transmit messages to each other, the operators switch is in the neutral position. Should the operator desire to transmit a message he throws his switch 25 upwardly to the "talk position and the divers switches either to the transmit position or the receive position. In general the latter switches will be in one of these-positions since the divers have been talking to each other. However, with the operators switch in the talk position the divers sound conversion units 41, 49, and 5| are all connected to the output coil 225.

With the operators switch in the talk position his speech currents fiow to the primary 233 of the input transformer 239 in a circuit which extends from the upper terminal of the operators sound conversion unit 3| through the conductor 323, the upper left-hand movable contact 325 of the operators switch 25, a corresponding fixed contact 335 now engaged, the conductor 285, the primary 233 of the input transformer 239, a conductor 293, an upper left-hand fixed contact 331 of the operators switch now engaged, the corresponding movable contact3|9, the conductor 32| to the lower terminal of the sound conversion unit.

The divers sound conversion units such as the unit 5| for which the switches arev thrown for reception are connected in the output of the amplifier 2|9 as is explained hereinabove. The divers sound conversion units such as the unit 41 for which the switch is thrown to the transmission side are now also connected to the output of the amplifier. In the latter case the circuit of the unit extends from the upper terminal of the secondary of the output transformer through the conductor 303, the conductor 3| a movable contact 229 of the switch H, the conductor 3|3, a central upper fixed contact 339 on the right of the operators switch 25, the corresponding movable contact 211, the conductor 215, a central lower fixed contact 34| on the right of the operatorss switch, the corresponding movable contact 2, the conductor 269, the movable contact 261 of the switch |9 thrown to the "transmit side, the sound conversion unit 41, the movable contact 30|, the conductor 299, the central lower movable contact 291 on the left in the operators switch, the corresponding fixed contact 295, the conductor 293, the upper central movable contact 29| on the left in the operators switch, a corresponding fixed contact 343 now engaging the movable contact, the conductor 33I, a movable contact 3230f the switch II, the conductor 333 to the lower terminal of the secondary 225 of the output transformer 245. r

If it becomes necessary for one reason or another to signal to the divers, the operator throws the operators switch 25 to the signal position immediately connecting the anode 29| of the oscillation generator tube 241 to the positive terminal of the source through the lower lefthand movable contact 345 of the operators switch. The oscillation generator 255 begins to operate and produces a signal which is supplied to the input of the amplifier 2|9 and after being amplified is impressed on the divers sound conversion units 41, 49, and 5| regardless of whether they are thrown to the transmit or receive position. Moreover the operator also hears the signal transmitted.

The divers sound conversion units which are thrown for reception are connected to the output of the amplifier as explained above. Those thrown to the transmission side are connected for reception through conductors connected to the secondary 225 of the output transformer 245 through the contacts'223 of switch l1 and through the lower central contacts 241 and 249 of the operators switch 25. The operators sound conversion unit 3| is also connected to receive the signal from the output of the amplifier 2|9 through the contacts 223 and the upper movable contacts 3|9 and 325 of the operators switch which are in the position shown in the drawings since the switch is thrown to the signal position.

Should the amplifier 2|9 become incapacitated for one reason or the other, the system may be sound powered. In this case the switch I! is thrown upward to the sound powered position connecting the sound conversion units 41, 49, and 5| in parallel through the movable contacts 223 and the fixed contacts 23|. For sound power operation the divers switches I9, 2|, and 23 must be thrown to the transmit position and the operators switch 25 must be at neutral. In this case the units 41, 49, and 5| are all connected to the conductors 283 and 285 leading to the input of the amplifier 2| 9. The circuit is com leted through the contactor 223 and conductors 3 3 and ,33I. The operator may listen by plugging in a receiver to a receptacle connecting the receiver in parallel with the other sound conversion units. Since all of the sound conversion units are of the batteryless telephone type provided with permanent magnets the sound produced by one of the operators speaking in his sound conversion unit operates the other units.

In the apparatus shown in Fig. 6 the transition from the power operated to the sound powered system is by hand. This is the most common method of operation. On occasions it may be desired to cause the transition to take place auto-- matically in response to the failure of the amplifier unit or certain of its parts. This object is accomplished as shown in Fig. 7 by providing a relay I, the exciting coil 353 of which is connected across the part of the amplifier unit, to the failure of which the automatic response is to take place. The most common source of failure is the cathode circuit and the coil 35l' is indicated as connected in the circuit. The relay is of the high impedance type so that the amplifier M3 is ,not shortcircuited. So long as the amplifier is energized the exciting coil 353 of the relay is energized and the relay is in a position in which one of its movable contacts 355 engages a plurality of fixed contacts 351 connected to the amplifier and sound units. The fixed contacts 351 correspond to the fixed terminals 221 of the power switch II. The movable contacts 355 of the relay are in turn vconnected to the terminals of the generator in the same manner as contacts 2H5.

Another set of movable contacts 353 is normally engaged with corresponding fixed contacts 35! connected to the amplifier output circuit. The movable contacts are connected to the operator's switch 25 in a manner similar to that in which the movable contacts 223 are connected to this switch. When the amplifier becomes deenergized by reason of some detect the relay "I is de-energized and the armature drops disconnecting the amplifier and sound units from the generator and the amplifier output from the operators switch 25. At the same time the lower set of movable contacts 353 of the relay engages another set of fixed contacts 363 which are connected to the amplifier input thus connecting the sound conversion units in parallel.

Although I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention, therefore, is not to be restricted except in so far as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. A system of communication'between a central station and a plurality of distributed stations comprising a sound conversion unit at each distributed station and at said central station, switching means individual to each distributed station providing for the transmission of a message from any one of said distributed stations to any other of said distributed stations and switching means associated with said central station providing for the reception of said messages by said central station and for the transmission of a message from said central station to said distributed stations, the last said switching means operating to permit the transmission of a message to said distributed stations when the switching means individual to said distributed stations is either in the transmitting or receiving position.

2. A system of communication between a central station located above water and a plurality of distributed stations located in diving suits under water comprising unitary sound conver sion units mounted in said diving suits in a position such that sound may be conveniently impressed thereon for transmission or received therefrom, sound conversion means located at said central station, switching means individual to each said sound conversion unit and located at said central station providing for the transmission of a message from any one of said distributed stations to any other of said distributed stations'and switching means assoclated'with and located at said central station providing for the reception of the said message from any one station to any other station and for the transmission of a message from said central station to said distributed stations, the last last switching means operating to' permit the transmission of a message from said central station to any distributed station when the switch individual to said station is either in the receiving or transmitting position. 7

3. A system of communication between a central station located above water and a plurality of distributed stations located in diving suits under water comprising unitary sound conversion units mounted in said diving suits in a position such that sound may be conveniently impressed thereon for transmission or received therefrom, signaling means, switching means individual to each said sound conversion unit and located at said central station providing for the transmission of a message'from any one of said distributed stations to any other of said distributed stations and switching means associated with and located at said central station providing for the reception of the said message from any one station to any other station and for the operation of said signal means to transmit a signal from said central station to said distributed stations, the last said switching means operating to permit the transmission of a signal from said central station to any distributed station when the switch individual to said station is either in the receiving or transmitting position.

4. A system of communication between a central station located above water and at least one distributed station located in a diving suit under water comprising a sound conversion unit mounted in said diving suit, signaling means including a discharge device having an anode, a cathode, and a control electrode, circuits between said anode and said cathode and said control electrode and said cathode inductively coupled to each other, means for connecting a dangerously high potential in one of said circuits, and a circuit for deriving energy from said first-named circuit, said last-named circuit being capable of metallic connection to said sound conversion unit and being insulated against metallic electrical conduction from said anode-cathode circuit.

5. A system of communication between a central station located above water and at least one distributed station located in a diving suit under water comprising a sound conversion unit mounted in said diving suit, signaling means including a discharge device having an anode, a cathode, and a control electrode, circuits between said anode and said cathode and said control electrode and said cathode inductively coupled to each other, means for connecting a dangerously high potential in one of said circuits, a circuit for deriving energy from said first-named circuits, said last-named circuit being insulated against metallic electrical conduction from said anode-cathode circuit, an amplifler having input and output circuits and common connections from said sound conversion unit and said last-named circuit to said input circuit, whereby said sound conversion unit is metallically connected to said last-named circuit.-

comprising unitary sound conversion units located at said distributed stations, sound conversion means located at said central station, an amplifier having input and output terminals, switch means to be actuated for connecting any one of said sound conversion units either to the input terminals or the output terminals of said amplifier whereby any one of said distributed stations may transmit a message to any other of said distributed stations and additional switch means for' connecting said sound conversion means to said input terminals, said switch means at the same time connecting said sound conversion units to said output terminals provided said first-named switch means has been actuated and regardless of whether said first-named switch means was initially actuated to connect said sound conversion units to said input terminals or said output terminals, whereby a message may be transmitted from said central station'to said distributed stations.

7. A system of communication between a plurality of distributed stations comprising unitary sound conversion units located at said distributed stations, an amplifier, having input and output terminals, switch means to be actuated for connecting any one of said sound conversion units either to the input terminals or the output terminals of said amplifier whereby any one of said distributed stations may transmit a message to any other of said distributed stations, an oscillation generator having inputand output circuits, said input circuit being open and said output circuit being permanently connected to said input terminals and additional switch means for simultaneously closing said output circuit and connecting said sound conversion units to said output terminals whereby a signal-may be transmitted from said central station to said distributed stations.

8. Apparatus according to claim '7 characterized by the fact that a dangerously high potential is impressed in the input circuit and the output circuit is completely insulated against metallic electrical conduction from the input circuit and the input terminals.

9. Apparatus for communication between a plurality of stations comprising sound conversion units, of the type including a permanent magnet and voice coil to be actuated in the field of said magnet, located at said stations, amplifying means to be connectedto said units for amplifying the output thereof, power supply means, means for connecting said amplifier to said power supply means and means for disconnecting said amplifier from said power supply means, responsive to a failure of said amplifying means, and for connecting the voice coils of said units in parallel, whereby signaling between said units is sound powered.

10. A system of communication between a central station located above water and a plurality of distributed stations located under water comprising unitary sound conversion units so disposed at said distributed stations that sound may be conveniently impressed thereon for transmission or received therefrom, sound conversion means located at said central station, switching means individual to each said sound conversion unit and located at said central station providing for the transmission of a message from any one of said distributed stations to any other of said distributed stations and switching means associated with and located at said central station providing for the reception of the said message from any one station to any other station and for the transmission of a message from said central station to said distributed stations, the last said switching means operating to permit the transmission of a message from said central station to any distributed station when the switch individual to said station is either in the receiving or transmitting position.

11. A system of communcation between a central station located above water and a plurality of distributed stations located under water comprising unitary sound conversion units so disposed at said distributed stations that sound may be conveniently impressed thereon for transmission or' received therefrom, signaling means, switching means individual to each said sound conversion unit and located at said central station providing for the transmission of a message from any one of said distributed stations to any other of said distributed stations and switching means associated with and located at said central station providing for the reception of the said message from any one station to any other station and for the operation of said signaling means to transmit a signal from said central station to said distributed stations, the last said switching means operating to permit the transmission of a signal from said central station to any distributed station when the switch individual to said station is either in the receiving or transmitting position.

12. A system of communication between a central station located above water and at least one distributed station located under water comprising a sound conversion unit at said distributed station, signaling means including a discharge device having an anode, a cathode, and a control electrode, circuits between said anode and said cathode and said control electrode and said cathode inductively coupled toeach other, means for connecting a dangerously high potential in one of said circuits, and a circuit for deriving energy from said first-named circuit, said lastnamed circuit being capable of metallic connection to said sound conversion unit and being insulated against electrical metallic conduction from said anode-cathode circuit.

13. A system of communication between a central station located above water and at least one distributed station located under water comprising a sound conversion unit at said distributed stations, signaling means including a discharge device having an anode, a cathode, and a control electrode, circuits between said anode and said cathode and said control electrode and. said cathode inductively coupled to each other, means for connecting a dangerously high potential in one of said circuits, a circuit for deriving energy from said first-named circuits, said lastnamed circuit being insulated against electrical metallic conduction from said anode-cathode circuit, an amplifier having input and output circuits and common connections from said sound conversion unit and' said last-named circuit to said input circuit, whereby said sound conversion unit is metallically connected to said last-named circuit.

14. A system of communication between a central station and a plurality of distributed stations located under water comprising unitary sound conversion units so disposed at said distributed stations that sound may be conveniently impressed thereon for transmission or received therefrom, sound conversion means located at said central station, switching means individual to each said sound conversion unit and located at said central station providing for the transmission of a message from any one of said distributed stations to any'other of said distributed stations and switching means associated with and located at said central station providing for the reception of the said message from any one station to any other station and for the transmission of a message from said central station to said distributed stations, the last said switching means operating to permit the transmission of a message from said central station to any distributed station when the switch individual to the last said station is either in the receiving or transmitting position.

15. A system of communication between a-central station and a plurality of distributed stations comprising unitary sound conversion units so disposed at said distributed stations that sound may be conveniently impressed thereon for transmission received therefrom, signaling means, switching means individual to each saidzsound conver-'- sion unit and located atsaid central station providing for the transmission of a message from any one of said distributed stations to any other or said distributed stations and switching means associated with and located at said central station providing for the reception 0! the said message from any one station to any other station and for the operation of said signaling means to transmit a signal from said central station to said distrib uted stations, the last said switching mean's operating to permit thetransmission of a signal from said central station to any distributed'station when the switch individual to said disributed station iseither in the receiving or transmitting position.

' 16. A system of communication between 'a central station and at least one distributed station 40 located under water comprising a sound conversion unit at said distributed station, signaling means including a discharge device having an anode, a cathode, and a control electrode, circuits between said anode and said cathode and said control electrode and said cathode inductively coupled to each other, means for connecting a dangerouslyhigh potential in one of said circuits, and a circuit for deriving energy from said firstnamed circuit, said last-named circuit being capable of metallic connection to said sound conversion unit and being insulated against electrical metallic conduction from said anode-cathode circuit.

1 17. A system of communication between a plurality of distributed stations located under water comprising a sound conversion unit at each said distributed station, signaling means including a discharge device having an anode; a cathode, and a control electrode, circuits between said anode and said cathode and said control electrode and said cathode, inductively coupled to each other, means for connecting a dangerously high potential in one ofsaid circuits, and a circuit for deriving energy from said first-named circuit, said last-named circuit being capable of metallic connection-to said sound conversion units and being insulated against electrical metallic conduction from said anode-cathode circuit.

18. A system of communication between a central station and at least one distributed station located under water comprising a sound conversion unit at said distributed station, signaling means including a discharge device having an anode, acathode, and a control electrode, circuits -:between said anode and said cathode and said control electrode and said cathode inductively coupledato each other,i.means for connecting a dangerously high potential in one of said circuits, a circuit for deriving energy from said firstnamed circuits,- said last-named circuit being insulated against electrical metallic conduction from said anode-cathode circuit,- an amplifier havingzinput and output circuits and common connections from said. sound conversion unit and said .last-namedcircuit tosaid input circuit.

whereby said sound conversion unit is metallicaily connected to said last-named circuit.

-' 19. A system of communication between a. plurality of distributed stations located under water comprising a soundconversion unit located at each said distributed station, signaling means including a discharge device having an anode, a cathode, and a control electrode, circuits between said anode and said cathode and said control electrode and said cathode inductively coupled to each other, means for connecting a dangerously high potential in one of said circuits, a

circuit for deriving energy from said first-named circuits, said' last-named circuit being insulated against electrical metallic conduction from said anode cathode circuit, an amplifier having input and output circuits and common connections from said sound conversion units and said lastnamed circuit'to said input circuit, whereby said sound conversion units are metallically connected to said last-named circuit.

20. Apparatus according to claim 4, characterized by a transformer having at least three coils functioning to couple the circuits between the anode and the cathode and the control electrode and the cathode and to supply the energy to the circuit for deriving energy from the anode cathode circuit.

' FIORENTINO G. 'IROISI. 

